A piezoelectric bulk wave device that includes a piezoelectric thin plate that is made of LiTaO.sub.3, and first and second electrodes that are provided in contact with the piezoelectric thin plate. The piezoelectric bulk wave device utilizes the thickness shear mode of the piezoelectric thin plate made of LiTaO.sub.3. The first and second electrodes are each formed by a conductor having a specific acoustic impedance higher than the specific acoustic impedance of a transversal wave that propagates in LiTaO.sub.3. When the sum of the film thicknesses of the first and second electrodes is defined as an electrode thickness, and the thickness of the piezoelectric thin plate made of LiTaO.sub.3 is defined as an LT thickness, the electrode thickness/(electrode thickness+LT thickness) is not less than 5% and not more than 40%.

An aspect of the present invention relates to a vibration element comprising: a substrate; a ceramic layer containing glass and provided on the substrate; and a piezoelectric element comprising an electrode layer fixed to the substrate with the ceramic layer therebetween and a piezoelectric layer, wherein the piezoelectric layer, the electrode layer, the substrate, and the ceramic layer are integrated by the piezoelectric layer, the electrode layer, the substrate, and the ceramic layer being sintered together at a sintering temperature of from 800° C. or higher to 940° C. or lower.

A piezoelectric element exhibiting a small leakage current density and high reliability as compared with a KNN thin film piezoelectric element in the related art is provided. The piezoelectric element is characterized by including a lower electrode, a piezoelectric layer primarily made from potassium-sodium niobate, which is a perovskite type compound represented by a general formula ABO.sub.3, and an upper electrode, wherein the piezoelectric layer is present between the lower electrode and the upper electrode, and the piezoelectric layer has the value determined by dividing the maximum value of intensity of a diffraction peak, where the angle of 2θ is within the range of 21.1°≦2θ≦23.4° in the X-ray diffraction pattern (2θ/θ), by the intensity of a diffraction peak, where 2θ is within the range of 30.1°≦2θ≦33.3°, of 0.04 or less.

A method for forming a pressure sensor includes forming a base of a sapphire material, the base including a cavity formed therein; forming a sapphire membrane on top of the base and over the cavity; forming a lower electrode on top of the membrane; forming a piezoelectric material layer on an upper surface of the lower electrode, the piezoelectric material layer being formed of aluminum nitride (AIN); and forming at least one upper electrode on an upper surface of the piezoelectric material layer.

Provided is a piezoelectric thin film device in which lattice mismatch between a piezoelectric thin film and a lower electrode layer (first electrode layer) is reduced. A piezoelectric thin film device 10 comprises a first electrode layer 6a and a piezoelectric thin film 2 laminated directly on the first electrode layer 6a; the first electrode layer 6a includes an alloy composed of two or more metal elements; the first electrode layer 6a has a face-centered cubic lattice structure; and the piezoelectric thin film 2 has a wurtzite structure.

A lead-free piezoelectric ceramic composition mainly includes a first crystal phase (KNN phase) and a second crystal phase (NTK phase). In the first crystal phase (KNN phase), a plurality of crystal grains formed of an alkali niobate/tantalate perovskite oxide having piezoelectric characteristics is bound to each other in a deposited state. The second crystal phase (NTK phase) is formed of a compound containing titanium (Ti) and fills spaces between the crystal grains in the first crystal phase.

To perform poling treatment in a simple procedure by dry process. A magnetic field poling device includes a first holding part configured to hold a film-to-be-poled (2); a second holding part configured to hold a magnet generating a magnetic field B to the film-to-be-poled (2); and a moving mechanism configured to move the first holding part or the second holding part in a direction perpendicular to the direction of the magnetic field B.

The present invention aims to provide a piezoelectric composition and a piezoelectric element. In the piezoelectric composition, the main component is represented by the following formula with a perovskite type structure,
(Bi.sub.(0.5x+y+z)Na.sub.0.5x).sub.m(Ti.sub.(x+0.5y)Mg.sub.0.5yMe.sub.z)O.sub.3
wherein, 0.05≦x≦0.7, 0.01≦y≦0.7, 0.01≦z≦0.6, 0.75≦m≦1.0, x+y+z=1 and the transition metal element Me is any one or more selected from the group consisting of Mn, Cr, Fe and Co.

A piezoelectric material contains: a first component which is a rhombohedral crystal in a single composition, has a Curie temperature Tc1, and is a lead-free-system composite oxide having a perovskite-type structure; a second component which is a crystal other than the rhombohedral crystal in a single composition, has a Curie temperature Tc2<Tc1, and is a lead-free-system composite oxide having a perovskite-type structure; and a third component which is a crystal other than the rhombohedral crystal in a single composition similar to the second component, has a Curie temperature Tc3≧Tc1, and is a lead-free-system composite oxide that has a perovskite-type structure and is different from the second component. When a molar ratio of the third component to the sum of the second component and the third component is α and α×Tc3+(1−α)×Tc2 is Tc4, |Tc4−Tc2|≦50° C.

A manufacturing method of an epitaxial thin film piezoelectric element includes: providing a substrate; forming a bottom electrode layer on the substrate by epitaxial growth process; forming a first piezoelectric layer that has c-axis orientation on the bottom electrode layer by epitaxial growth process; forming a second piezoelectric layer that has c-axis orientation and different phase structure from the first piezoelectric layer on the first piezoelectric layer by epitaxial growth process; and forming a top electrode layer on the second piezoelectric layer. The thin film piezoelectric element has good thermal stability, low temperature coefficient and high piezoelectric constant.